1. Field of the Invention
This invention relates generally to separator apparatus, and more particularly to a separator for purifying spent emulsions, such as cooling lubricants, or cleaning solutions, for example.
2. Discussion of Related Art
One example of such a separator can be found in Ullmanns Enzyklopadie der technischen Chemie, Verlag Chemie, Weinheim 1976, 4th Edition, Vol. 2, pages 217 to 220. Such separators are used for purifying or cleaning contaminated and spent emulsions, by removing therefrom foreign oils, finely disbursed solids, and other contaminants. Examples of emulsions so cleansed are cooling lubricants, cleaning solutions, and other types of emulsions. In the removal or separation process in such separators, the spent emulsion is processed to separate therefrom foreign oil, and sludge. Accumulated sludge must be periodically removed. In self-emptying separators the sludge is automatically removed or discharged by periodic flushing of the associated separator drum. Flushing times are typically empirically determined. In non-self-emptying separators, the sludge or solids must be manually removed from the separator drum, after periods of operating time that are typically determined via trial and error.
Since, in self-emptying separators, the emptying time is empirically determined and the operation of the separator must not be adversely affected by variations in the solids component, even at high solids concentrations, the capacity of the separator to accommodate the solids cannot be utilized and the separator has to be prematurely emptied for safety reasons. The solids filling capacity of the separator drum is therefore utilized to only a minimal extent.
If, on the other hand, a non-self-emptying separator fully laden with sludge is left to continue operating, the liquid, for example the cooling lubricant emulsion, is returned without effective purification to the machine to be cooled and lubricated.
Both these state-of-the-art separator systems have the disadvantage that any other malfunction of the separator or the system as a whole, which adversely affects the effectiveness of the separator, is neither detected nor indicated.
3. Summary of the Invention
An object of the invention is to provide an improved separator for purifying or cleaning contaminated and spent emulsions.
Another object of the invention is to provide an improved separator capable of operating for extended periods of time without requiring the emptying of sludge from the drum, while maintaining the quality of the regenerated emulsion throughout the extended operating time.
Another object of the invention is to increase the reliability of separators for regenerating spent emulsions.
In a separator of the type mentioned at the beginning, this problem is solved by a fine filter arranged in the outlet pipe for retaining residual solids, and means for measuring the pressure difference between the entrance and exit of the fine filter, and for generating a signal if a predetermined pressure difference is exceeded. The fineness of the fine filter and the predetermined pressure difference correspond to the predetermined quality of the emulsion.
Although processes for separating emulsions and solids are known from DE 35 23 907 Al, US 4,822,484, DE 28 10 306 C2, according to which the quality of separation of the emulsion into its constituents is monitored and automatically controlled by measurement of various physical parameters of the emulsion or one of its constituents, for example density, viscosity, conductivity, in conjunction with the use of centrifuges or hydrocyclones, measurement of the pressure difference at a filter is not used in any of these patents to monitor and control separation of the emulsion.
According to the invention, the quality of the emulsion flowing off from the separator is monitored, and any reduction in quality is detected by the generation of a signal. The fineness of the fine filter and the predetermined pressure difference can be empirically determined. The basis of one embodiment of the invention is that the residual solids which are not separated in the separator drum are retained by the fine filter so that the permeability of the filter decreases. This reduction in permeability is detected by measurement of the pressure difference.
After each response of the measuring arrangement, the fine filter has to be cleaned or the filter cartridge replaced. Accordingly, a backwashing unit actuated by the signal from the measuring means for automatically backwashes the fine filter. This is because the fine filter can be cleaned during operation without the separator drum having to be switched off.
Although it is known from the book "Messen und Regeln in der Chemischen Technik (Measurement and Control in Chemical Engineering)", edited by F. Hengstenberg, B. Sturm and O. Winkler, Springer Verlag, Berlin 1964, page 1428, that the pressure drop at a filter can be measured for the purpose of controlling physical/chemical equipment by compressed air (the filter is used to pick up unwanted particles of dirt present in the compressed air), the manometers incorporated in the system are only used for rapid testing of the pressure and not for indicating fouling of the filter.
An indicator actuated by the signal from the measuring means is also included for indicating that the separator has typically emptied of sludge. A sludge emptying operation to be carried out much earlier on safety grounds is avoided.
In a self-emptying separator, it is of further advantage if the sludge emptying operation is initiated by the signal from the measuring means. In a non-self-emptying separator, the separator is switched off by the signal from the measuring arrangement. In such a case, the separator has to be emptied by hand.
In another embodiment of the invention, a delay circuit is incorporated in the measuring means so that, after the separator has started up, the measuring means can be switched on after a certain interval. This is because, when the separator drum is started up, any residual soil present is discharged which would lead to an increase in pressure at the fine filter and hence to a false signal from the measuring arrangement. Such false alarms or signals are avoided by the above-mentioned measure. The time interval in question may be about five minutes.
Another advantage of the separator according to the invention is that malfunctions adversely affecting the quality of the emulsion are recorded irrespective of their cause.